This is an improved printer circuit and method for creating relatively high output resolution for text while maintaining a relatively low clock speed for the color circuits, and more specifically, is a circuit for first generating a plurality of overlapping output color bits in parallel, and second, using font mask data to decide which color bits are to be used within the mask, and outside the mask, to generate the final output.
There are commercial printers in use which can print halftoned images, computer graphics, text and other forms of visual data on a single page. Some forms of data, such as a halftoned color, have a low frequency dot clock and low resolution, but many bits per dot. Others, such as character outlines, have only one bit per pixel, but require high resolution at the edges, and a higher clock rate. The text color and background colors are typically multiplexed using the font outline as a controlling mask, and in order to preserve all of the attributes of both of the inputs, the output data must be produced at the higher bit rate. U.S. Pat. No. 5,225,911 describes such a system, and is incorporated by reference herein. More specifically, if the edge of a character of one color falls somewhere inside the boundary of a background dot of another color, the circuit must produce two partial dots to preserve the quality of the outline, one of the text character color for the portion of the dot that is inside the character, and the other of the background color for the portion of the dot that is outside the character. An improved method for performing this function while allowing the color generating circuit to proceed at the lower clock speed is needed.